The present invention relates generally to motor vehicles. More particularly, the invention relates to a strategy for determining a vehicle payload condition.
Vehicle dynamic behavior may be significantly affected by vehicle loading condition. One known method of estimating vehicle payload is based on pressure measurements in the air springs of self-leveling suspensions. Few vehicles, however, are equipped with self-leveling suspensions and even fewer feature pressure sensors. On the other hand, active safety systems, which require sensors measuring vehicle dynamic response, are becoming more common. For example, many modern vehicles are equipped with vehicle stability enhancement (VSE) systems, which include lateral acceleration sensors. Anti-rollover systems use roll rate sensors in order to evaluate rollover danger and either to apply brakes (in order to reduce probability of rollover) or to deploy passive safety restraints if rollover is deemed imminent. Vehicles with electronically controlled suspensions (e.g. semi-active suspensions) often utilize suspension deflection sensors, which measure relative position of wheels with respect to the body.
Vehicle dynamic response to driver steering and braking inputs, in particular roll, pitch and yaw responses, may be significantly affected by vehicle payload. Therefore, several chassis control systems may significantly benefit from information regarding vehicle payload. For example, brake force distribution may be made dependent on payload conditions, thus improving braking efficiency and reducing stopping distance under a variety of loading conditions.
Active chassis systems, which control vehicle response in the yaw plane, such as VSE and active rear steer systems, typically utilize a vehicle reference model, which generates desired vehicle response. These systems may benefit by adapting the reference model to payload conditions in order to improve performance and/or reduce unnecessary activations. Electronically controlled suspensions generally require estimation of body motions, which may be improved if knowledge of payload conditions were available; this in turn may bring about performance improvements. It would therefore be beneficial to provide a strategy for determining vehicle payload condition using sensor information that becomes more widely available in modern vehicles.
Accordingly, it would be desirable to provide a strategy for determining vehicle payload condition that overcomes the aforementioned and other disadvantages.
A first aspect of the present invention provides a method of determining a vehicle payload condition. The method includes determining a first payload-state parameter, a second payload-state parameter, and at least one roll value. A first differential is determined based on the first payload-state parameter and the second payload-state parameter. A second differential is determined based on the first payload-state parameter and the roll value. A multiplier is determined. A payload estimate is determined based on the first payload differential, the second payload differential, and the multiplier.
A second aspect of the invention provides a computer usable medium including a program for determining a vehicle payload condition. The computer usable medium includes computer readable program code for determining a first payload-state parameter, a second payload-state parameter, and at least one roll value. The computer usable medium further includes computer readable program code for determining a first differential based on the first payload-state parameter and the second payload-state parameter, determining a second differential based on the first payload-state parameter and the roll value, determining a multiplier, and determining a payload estimate based on the first payload differential, the second payload differential, and the multiplier.
A third aspect of the invention provides a system for determining a vehicle payload condition. The system includes means for determining at least one roll value, means for determining a first payload-state parameter and a second payload-state parameter, means for determining a first differential based on the first payload-state parameter and the second payload-state parameter, and means for determining a second differential based on the first payload-state parameter and the roll value. The system further includes means for determining a multiplier and means for determining a payload estimate based on the first payload differential, the second payload differential, and the multiplier.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention, rather than limiting the scope of the invention being defined by the appended claims and equivalents thereof.